In underjet coke ovens, nozzle plate constructions are provided for distributing and metering combustion-supporting air supplied upwardly to the regenerators through a sole flue which extends parallel to the coke oven chamber axis. The sole flue is closed at its top by plate elements which are disposed in end-to-end relationship. The plate elements are usually supported by side ledges of the so1e flue and are provided with apertures through which air can pass from the sole flue to the regenerators. Depending on the cross-sectional area of the apertures, the amount of combustion-supporting air supplied to the regenerators can be controlled; and in this respect the nozzle plate constructions act as valves.
One of the main requirements in coke oven heating is uniform metering and distribution of the combustion-supporting air with an accuracy that meets the requirements of combustion technology. In practice, there are considerable difficulties encountered in meeting these requirements. In an underjet oven, the combustion-supporting air which must be preheated flows from a sole flue below the regenerator into the voids of the regenerator bricks. To insure that the combustion-supporting air is distributed properly, plates of the type described above have been provided in the top part of the sole flue, the plates being formed with apertures of different sizes as a means of controlling air distribution. An arrangement of this type is disclosed, for example, in U.S. Pat. No. 3,252,872.
Plates formed with apertures of different sizes, however, have a number of unsatisfactory features. The main disadvantages are uneven and difficult distribution of the combustion-supporting air. The required quantity of air can be adjusted only by trial and error, a difficult, time-consuming and expensive procedure. Moreover, due to lack of seals, cross-flows occur between the various regenerator portions and may be responsible for uncontrolled interaction affecting air distribution in the various portions.